Ground-plane-less bidirectional terahertz absorber based on omega resonators.

We present a new ultrathin metamaterial that acts as a frequency-selective absorber of terahertz radiation. The absorber is a square array of pairs of omega-shaped micro-resonators made of high-ohmic-loss metal. The metamaterial provides significant suppression of transmitted and reflected radiation in a bidirectional regime (that is, for both forward and backward propagating radiation).

Broadband infrared quarter wave plate realized through perpendicular-to-helical-axis wave propagation in a helix array.

The ability of helix arrays to filter circularly polarized light efficiently when the light propagates parallel to the helical axis has been demonstrated recently. In this Letter, we present a broadband linear-to-circular polarization transformer composed of metal microhelices. The device provides significant transformation performance combined with high transmittance over a broad infrared wave band.